'Old Sultan' is not one of the Brothers Grimm's, the authors that immediately spring to mind along with Hans Christian Andersen when thinking of fairy/folk tales, best or most iconic collected stories. Only because there are so many great stories of theirs, and their collected ones, because 'Old Sultan' is sweet and immensely charming with characters that do stick in the mind and likewise with the message it has. It does deserve to be better known than it is.
Although 'Simsala Grimm's' version is a recommended watch, personal opinion of course, do consider 'Grimm Masterpiece Theater's' (or to some 'Grimm's' Fairy Tale Classics') version even better. A great way to get introduced to the story and a great episode on its own, one of the best of this interesting anime series based on their stories that, despite the music and voice acting not always being great, is worth watching especially if for watching adaptations of lesser known works for the first time.
Really very little to dislike really. Preferably would have liked a more subtle voice for the wolf, the more abrasive quality to his voice didn't always fit the character design (though there are far worse instances in the series) to my liking.
That nit pick aside, so much works in 'Old Sultan's' favour. The animation is full of rich colour and the attention to detail in the backgrounds is lovely to see. The character designs don't quite have the same amount of finesse but is smooth and detailed enough, the titular character particularly. Am not always a fan of the music on the series, but here it is a good fit, it's whimsical and atmospheric and there is less of the stuck in the 80s feel that can be found in the series. Other than some reservations with the wolf at times, also didn't have a problem with the voice acting. The narrator, of whose narration succeeds in moving things forward and not over-explaining, fares best, while the best voiced character is the cat.
Writing avoids over-simplicity and convolution while showing remarkable maturity. The storytelling has every ounce of the charm of the original story, with a beautifully characterised friendship that has depth, a non-cliched and quite powerful ending and a message that resonates without being didactic. The characters are handled well, the cat is hilarious and the wolf is very likeable and adorable. The titular character is not as likeable but he is the sort of character that grows and that growth convinces.
Altogether, great. 9/10